1. Field of the Invention
The present invention relates to grinding bit apparatus used in connection with grinding machines, particularly grinding machines of the class used for performing operations on stained glass panes. The present invention more particularly relates to an improved grinding bit apparatus having improved operational flexibility and improved operational performance.
2. Description of the Prior Art
Grinding machines generally incorporate a frame supporting a work holder or work table, a prime mover connected with the frame, a drive shaft connected with the prime mover, and a grinding bit connected with the drive shaft for performing a grinding operation on a workpiece. Variations on this scheme are plentiful, and the grinding bit may have various configurations ranging from an elongate cylindrical shape mounted axially with respect to the drive shaft to a wheel shape mounted horizontally with respect to the drive shaft.
In many instances, the heat generated from the grinding operation is excessive to the point that provision must be made for its removal and/or control. In these instances, air or water is fed to the grinding bit in order to serve as a coolant. Also, certain operations may benefit directly from the introduction of wash water on the grinding bit as an aid to the grinding process being performed on the workpiece.
There are a number of examples of grinding machines employing grinding bits which are cooled by water. U.S. Pat. No. 1,827,688 to Ley, dated Oct. 13, 1931, discloses a grinding machine utilizing a water reservoir beneath the bit and a screw-like formation located in the reservoir for spraying water up onto the grinding bit. U.S. Pat. No. 2,110,441 to Kasch, dated Mar. 8, 1938, discloses a grinding machine utilizing a grinding bit which is supplied with water coolant via operation of a propeller-shaped member located in the water reservoir beneath the grinding bit. U.S. Pat. No. 2,457,283 to Slatter, dated Dec. 28, 1948, discloses a grinding machine having a cup-shaped grinding bit cooled by water from a reservoir that is driven up a duct therein, and further having a tool holder in the form of an adjustable head supported on a standard adjacent the grinding bit. Finally, U.S. Pat. No. 2,489,437 to Sandoz, dated Nov. 29, 1949, discloses a grinding machine having a spindle carrying a grinding bit in which water is used to cool the spindles and cool the grinding bit as it makes its way flowably thereto.
Grinding machines used to shape glass panes, such as glass panes used in the making of stained glass works, are provided with a vertical drive shaft to which is connected a cylindrically shaped bit, a work table for holding the glass pane perpendicularly with respect to the bit, and water transfer means to serve as a coolant and particle wash during the grinding operation. In this regard, the artisan's hand moves the glass pane on the work table into selective engagement with the grinding bit so as to achieve a desired finished product.
There are various structures known in the prior art to provide water to the bit during a grinding operation. One structure utilizes a sponge which partly rests in the water reservoir and makes contact with the grinding bit. While this structure is simple and inexpensive, it is subject to excessive wear may be accidentally knocked out of position, may not provide an adequate water supply to the grinding bit, and because the sponge accumulates particles during grinding, periodic cleaning thereof is required.
One grinding machine which provides a mechanically induced supply of water to the grinding bit is disclosed in U.S. Pat. No. 4,516,357 to Gach, dated May 14, 1985. In this grinding machine, coolant water is supplied to the grinding bit by an impeller mounted to the drive shaft. A prime mover in the form of an electric motor drives the drive shaft from a location below the water reservoir, the drive shaft protruding vertically up from the reservoir. Below the grinding bit, and located within the reservoir, is an impeller rotatable with the grinding bit. Surrounding the impeller and the lower portion of the grinding bit is an annular collar that depends from the underside of a work table. In operation, when the drive shaft rotates, the impeller drives water from the reservoir up toward the working surface of the grinding bit, and the annular collar helps to contain the water driven by the impeller. At the top of the annular collar, whereat is provided a grinding bit opening in the work table, a frustoconical bevel (oriented upwardly toward the grinding bit) directs the coolant onto the working surface of the grinding bit.
The aforesaid device disclosed in U.S. Pat. No. 4,516,357 has the advantage of being able to supply water from a reservoir for cooling and washing of the grinding bit without the need for a sponge or complicated pumping and piping that may be otherwise present in industrial grinding machines. However, certain disadvantages still pertain. For example, the various impellers disclosed therein all have structures which serve to splash water toward the grinding bit by a general agitation of the water in the reservoir. This is inefficient and results in a poor water transfer rate compared with the amount of agitation that is produced in the reservoir. Further, there is no provision for axial adjustment of the work surface of the grinding bit relative to the work table so that wear-out of the grinding bit can be extended across the entire grinding surface of the grinding bit. Finally, there is no provision for replacement of the grinding bit with other sized grinding bits, in which certain of these grinding bits could perform other operations, such as drilling.
Importantly, too, prior art impellers, such as that disclosed hereinabove, will not raise water from the reservoir to a height above the work table. This limits the location of the grinding bit to a height only at the work table, thereby preventing the use of small diameter grinding hits which must, because of their small diameter, be mounted at the end of the drive shaft at a height above the work table.
Accordingly, what is needed is a grinding machine, particularly a grinding machine adapted for use with pane glass, which has none of the disadvantages of U.S. Pat. No. 4,516,357 discussed hereinabove.
In the prior art there are several examples of grinding machines which disclose structures of interest. For instance, U.S. Pat. No. 3,775,908 to Meckler et al, dated Dec. 4, 1973, discloses a grinding machine particularly adapted for spectacles glass grinding having a fine grinding bit and a rough grinding bit arranged together on a bushing which is axially displaceable on the drive shaft of the machine. And further for instance, U.S. Pat. 4,446,657 to Asaeda et al, dated May 8, 1984, discloses a grinding bit having a sealing layer between the grinding portion thereof and the support portion thereof so that coolant water cannot penetrate into the support portion. And still further for instance, U.S. Pat. No. 4,558,538 to Green, dated Dec. 17, 1985, discloses a sander having a bit in the form of a sleeve covered by sandpaper which is axially supported at both ends by an arbor; the sleeve is axially positionable along the arbor so as to provide fresh bit surface as needed for sanding operations. Yet none of these offers solutions adoptable to provide a grinder machine of the type needed.